1. Field of the Invention
The present invention relates to a sidelight-type spread illuminating apparatus including a light guide plate that has a light source disposed at an incident light end surface thereof and emits illumination light in a spread pattern from an emitting surface.
2. Description of the Related Art
As an illumination unit for a liquid crystal display panel, a sidelight-type spread illuminating apparatus (backlight) in which LEDs that are compact and have excellent environmental suitability are disposed along a side end surface of a light guide plate is widely utilized. As shown in a spread illuminating apparatus 100 illustrated in FIG. 5, in a constitution of such a spread illuminating apparatus that is regularly used in order to dispose a plurality of LEDs 102 along a side end surface 101c of a light guide plate 101, a forward portion of a rectangular strip-shaped flexible printed board (hereinafter also referred to as an FPC) 105 on which the plurality of the LEDs 102 are mounted is fixed using a double-sided tape 106 to one principal surface 101b of the light guide plate 101.
However, the double-sided tape 106 is generally formed by applying a transparent adhesive that is acrylic-based, silicone-based, or the like to both surfaces of a transparent substrate such as a PET film. Thus, in such an arrangement, there has been a problem in that optical loss may occur when light emitted from the LEDs 102 progresses into portions of the double-sided tape 106 disposed in front of the LEDs 102, leading to brightness reduction of the spread illuminating apparatus 100.
The applicant of the present application previously proposed a spread illuminating apparatus that overcomes the above-described problem by configuring the LEDs as point light sources and disposing a plurality of these LEDs such that they are separated from each other along a side end surface of the light guide plate (for example, refer to Japanese Patent Application Laid-Open (JP-A) No. 2005-259374). As shown in FIG. 6, in this spread illuminating apparatus 110, double-sided tapes 116, 117, 118, and 119 that adhere an FPC 115 to one principal surface 111b of a light guide plate 111 are arranged intermittently in regions excluding the portions in front of LEDs 112, 113, and 114. Thereby, in the spread illuminating apparatus 110, the amount of light that progresses into the double-sided tapes 116, 117, 118, and 119 after being emitted from the LEDs 112, 113, and 114 is reduced compared to the spread illuminating apparatus 100 shown in FIG. 5, and thus reductions in brightness of the spread illuminating apparatus 110 can be suppressed.